Renting a car in Italy

Yes, you need an International Driver's License for Italy.
Go to Autoeurope.com to see the closest car rental pick up in Italy. Take public transportation or taxi to cross the border from Switzerland.You do not want to pick up a car inn country and drop it off in another as there are high drop off fees.
You really need a car to explore the hill towns in Tuscany.

Yes, you do need an IDP in Italy. It's the law.

Not knowing your itinerary and first stop that requires a car, hard to say where you should rent one.

Again, which towns you want to see in Tuscany and whether train or car is necessary is questionable.

Lucca, Montecatini Terme, Pisa, Pistoia easily done by train.

Volterra and San Gimignano and Siena by bus.

As a rule anything south of Florence will require a car.

Keim, please be aware that, as far as I know, there is no such thing as an International Drivers License. You are required to have an International Drivers Permit (IDP), which is a translation of your own driver’s license, and to also carry your own driver’s license. I don’t know where you live, but in the US you can easily get an IDP at any AAA office, for about $15 plus 2 passport-type photos, or get photos taken there for an additional fee. While the IDP is legally required in Italy, for each driver, the rental office may or may not ask to see it, they will certainly want to see your own license. However, if you are stopped by police, and/or have an accident, you will need to show both your license and IDP, or else be in deep doo-doo for not following the law.

"We plane on doing the usual stops ending in Rome, including the countryside. "

If you clarify exactly what you mean by this, people can give you specific advice on where to pick up and return a car. Which places are you definitely visiting and which places are you possibly visiting? Since a car is a great help in the countryside but a great hindrance in cities, the particulars of your trip are necessary for people to give you the best help.

If you have a license from an EU country, you do not need an IDP. Otherwise, you need one.

Keim,

As the others have mentioned, unless you have an E.U. driver's license you will need the compulsory International Driver's Permit. Your profile doesn't indicate where you're located, so the specifics on getting an IDP may vary if you're not located in the U.S. or Canada.

If this is your first time driving in Italy, it would be prudent to do some research on ZTL (limited traffic) zones which exist in many Italian towns. Each pass through one of these areas will result in hefty fines, which you probably won't know about until several months after you return home, and unexplained charges start to appear on your credit card. There are also a few other "caveats" such as driving in bus lanes, the Traffic Tutor on motorways, etc.

I am planning on picking the car up in Florence for our Tuscany stops. Then dropping it off in Rome.
Is that smart? Could i pick it up in Siena then drop it off somewhere before Rome? Thoughts?

You could drop the car off either at Chiusi or at Orvieto.